This invention relates to processing whole blood into fractions and, more particularly, to improvements in blood processing systems for separating platelet-rich plasma from autologous blood.
The science and effectiveness of using platelet-rich plasma derived from the patient""s own blood in surgery are documented in medical, trade, and science journals. A known method for the preparation of platelets from whole blood is described in the American Association of Blood Bank""s Technical Manual, 12th Edition, 1996, at pages 700-701, Method 9.11. A system employing this method collects the patient""s whole blood into a collection unit with two integrally attached transfer containers. The blood is collected into the collecting container, the other two transfer containers are collapsed, and the two transfer containers with the collecting container are subjected to a xe2x80x9csoft spinxe2x80x9d in a centrifuge, which brings the plasma to the top of the collecting unit, leaving red cells at the bottom. In the next step, the collecting container containing the blood fractions are squeezed in a plasma extractor to force the platelet-rich plasma into one of the transfer containers through a connecting tube. A fraction comprising red cells remains behind in the collecting container, which is then removed. Next, the two transfer containers, the first being empty and the second containing the plasma, are subjected to a xe2x80x9cheavy spinxe2x80x9d in a centrifuge to concentrate platelets at the xe2x80x9cbottomxe2x80x9d of the second transfer container, leaving a platelet-poor fraction of the plasma (PPP) above the platelet concentrate (PC) in the second transfer container. The following step squeezes the second transfer container to express the PPP into the first transfer container. The platelet concentrate (PC) is then resuspended and collected for use. This system uses a process requiring six separate steps, including two centrifugal steps and two separation steps. The terms xe2x80x9clight spinxe2x80x9d and xe2x80x9cheavy spinxe2x80x9d are defined in Table 10.5-1 at page 716 of the AABB Technical Manual.
An alternative method of separating blood fractions is discussed in U.S. Pat. No. 5,102,407 and referred to as the xe2x80x9cAmsterdamxe2x80x9d method. Instead of two spins, soft then hard, as discussed above, a single hard spin is used in which three fractions are separated, that is, a relatively platelet-free plasma, red blood cells, and an intermediate xe2x80x9cbuffy coatxe2x80x9d layer which contains platelets and leukocytes.
The usual procedures often employ pliable plastic bags which make it difficult to separate the blood fractions accurately. Consequently, improvements have been needed. The present invention is embodied in a new blood separation kit which provides a more convenient and efficient means for separating a patient""s blood and in particular for recovering platelets.
The invention provides a single use system for separating blood and preferably for producing platelet concentrates (PC). In one embodiment, the system is in the form of a syringe kit including disposable components supplied in sterile disposable packaging, and having all of the components required to draw blood from the patient, prevent blood coagulation, separate the sample into fractions including platelet concentrate, and deliver the platelet concentrate to a surgical site. More precise separation of the separated blood fractions is possible, compared to the results achieved with pliable plastic bags. Such a system will be useful to medical and dental practitioners.
The invention may be generally described as including an elongated container, preferably cylindrical, which is adapted to be placed in a centrifuge for separating the fractions of blood introduced into the container. The container is equipped with a first port through which the blood fractions can be expelled by a plunger movably fitted within the container. The first port is located at a first end of the container and a second port is located on the movable plunger. Both ports are normally closed and they are opened from outside the container as required for removal of blood fractions. The plunger is equipped with a detachable hollow plunger rod adapted to open the second port when the plunger rod is attached to the plunger. A third port is mounted at the end of the plunger rod, the third port also is normally closed unless opened from outside the plunger rod.
In one embodiment of the invention, the container is in the form of a syringe barrel fitted with a moveable plunger. The syringe barrel is charged with a patient""s blood and all of the centrifugal and separation steps are performed while the blood is in that container. The syringe barrel is adapted for use in a centrifuge, and has valves fitted at one end and within the plunger, making it possible to collect blood, centrifuge the blood in the syringe barrel, expel red blood cells after the first or soft spin, centrifuge the remaining platelet-rich plasma and expel platelet-poor plasma after the second or hard spin. The platelet concentrate remains in the syringe barrel, where it can be resuspended in a medium or media that can be introduced into the container through one of the valves.
In another embodiment, the container of the invention is given a xe2x80x9chardxe2x80x9d spin, omitting the xe2x80x9csoftxe2x80x9d spin. Three fractions are formed, the first fraction, the red blood cells, is expelled through the first port, then the second fraction, platelet-poor plasma, is expelled through the second and third ports, leaving the third layer, consisting of platelets and plasma, for further processing.
The separation of blood fractions may be carried out manually after centrifuging the whole blood in the container. Alternatively, the separation of blood fractions could be carried out automatically in centrifuge equipment having facilities for opening the ports after it has been determined that the desired separation has been made.
Associated with the container preferably will be a needle assembly for drawing a patient""s blood and which is adapted to transfer the blood into the syringe container directly or into a separate container for subsequent transfer into the syringe container. One or more waste bags adapted to receive platelet-poor plasma and red blood cells from the syringe cylinder after the soft and hard spins may be part of the syringe kit.